A stepwise approach to cardiac risk assessment and stratification in patients undergoing noncardiac surgery is illustrated in Fig. 467-1. The evaluation begins with characterization of the combined surgical and clinical risk into categories of low (<1%) and elevated risk for major adverse cardiovascular events (MACE). Select surgeries are associated with very low risk for MACE; these surgeries and procedures include select ophthalmologic surgeries (e.g., cataract surgery), select endoscopic procedures, and select superficial procedures. Patients undergoing these low-risk procedures should proceed to surgery without further testing. Clinical risk may be estimated with the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) risk calculator (http://www.riskcalculator.facs.org) or with calculation of the Revised Cardiac Risk Index (RCRI).
Composite algorithm for cardiac risk assessment and stratification in patients undergoing noncardiac surgery. Preoperative evaluation involves a stepwise clinical evaluation. Those individuals requiring emergency surgery should proceed without further risk stratification. Acute coronary syndrome (step 2) should be evaluated and treated, accordingly to goal-directed medical therapy. For patients awaiting non-emergent surgeries and without acute coronary syndrome, perioperative risk is a combination of clinical and surgical risk. Select procedures and surgeries (e.g., select endoscopic procedures) are associated with low perioperative (<1%) risk and no further clinical testing is generally necessary. For those procedures associated with elevated risk, an assessment of functional capacity informs the decision for further testing. Those individuals with moderate or greater functional capacity do not require further testing and should proceed to surgery. Individuals with poor or unknown functional capacity may require pharmacologic stress testing if it would change decision-making or perioperative care. (From LA Fleisher et al: Circulation 2014;130:e278-e333, with permission.)
Previous studies have compared several cardiac risk indices. The American College of Surgeons’ National Surgical Quality Improvement Program prospective database has identified five predictors of perioperative myocardial infarction (MI) and cardiac arrest based on increasing age, American Society of Anesthesiologists class, type of surgery, dependent functional status, and abnormal serum creatinine level. However, given its accuracy and simplicity, the RCRI (Table 467-2) is often the favored risk index. The RCRI relies on the presence or absence of six identifiable predictive factors: high-risk surgery, ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetes mellitus treated with insulin, and renal insufficiency with a creatinine >2.0 mg/dL. Each of these predictors is assigned one point. The risk of major cardiac events—defined as MI, pulmonary edema, ventricular fibrillation or primary cardiac arrest, and complete heart block—can then be predicted. Based on the presence of none, one, two, three, or more of these clinical predictors, the rate of development of one of these four major cardiac events is estimated to be 0.4, 0.9, 7, and 11%, respectively (Fig. 467-2). An RCRI score of 0 signifies a 0.4–0.5% risk of cardiac events; RCRI 1, 0.9–1.3%; RCRI 2, 4–7%; and RCRI ≥3, 9–11%. The clinical utility of the RCRI is to identify patients with three or more predictors who are at very high risk (≥11%) for cardiac complications and who may benefit from further risk stratification with noninvasive cardiac testing, initiation of preoperative preventive medical management, or avoidance of surgery.
TABLE 467-2Clinical Markers Included in the Revised Cardiac Risk Index ||Download (.pdf) TABLE 467-2 Clinical Markers Included in the Revised Cardiac Risk Index
|High-Risk Surgical Procedures |
|Vascular surgery (except carotid endarterectomy) |
|Major intraperitoneal or intrathoracic procedures |
|Ischemic Heart Disease |
|History of myocardial infarction |
|Current angina considered to be ischemic |
|Requirement for sublingual nitroglycerin |
|Positive exercise test |
|Pathological Q-waves on ECG |
|History of PCI and/or CABG with current angina considered to be ischemic |
|Congestive Heart Failure |
|Left ventricular failure by physical examination |
|History of paroxysmal nocturnal dyspnea |
|History of pulmonary edema |
|S3 gallop on cardiac auscultation |
|Bilateral rales on pulmonary auscultation |
|Pulmonary edema on chest x-ray |
|Cerebrovascular Disease |
|History of transient ischemic attack |
|History of cerebrovascular accident |
|Diabetes Mellitus |
|Treatment with insulin |
|Chronic Renal Insufficiency |
|Serum creatinine >2 mg/dL |
Risk stratification based on the revised cardiac risk index; derivation and prospective validation of a simple index for prediction of cardiac risk in patients undergoing major noncardiac surgery. Cardiac events include myocardial infarction, pulmonary edema, ventricular fibrillation, cardiac asystole, and complete heart block. (Adapted from TH Lee et al: Circulation 100:1043, 1999.)
For patients at elevated combined clinical and surgical risk for MACE, the stepwise perioperative cardiac assessment for coronary artery disease (CAD) proceeds with consideration of functional capacity. Participation in activities of daily living offers an expression of functional capacity, often expressed in terms of metabolic equivalents (METs). For predicting perioperative events, poor exercise tolerance has been defined as the inability to walk four blocks or climb two flights of stairs at a normal pace or to meet a MET level of 4 (e.g., carrying objects of 15–20 lb or playing golf or doubles tennis) because of the development of dyspnea, angina, or excessive fatigue (Table 467-3). Patients with moderate or greater (≥4 METs) functional capacity (e.g., climbing up a flight of stairs, walking up a hill, or walking on level ground at 4 mph) generally should not undergo further non-invasive cardiac testing prior to elective non-cardiac surgery. Those patients with poor (<4 METs) or unknown functional capacity should undergo pharmacological stress testing if the results of such testing would impact decision-making or perioperative care.
TABLE 467-3Assessment of Cardiac Risk by Functional Status ||Download (.pdf) TABLE 467-3 Assessment of Cardiac Risk by Functional Status
• Has difficulty with adult activities of daily living
• Cannot walk four blocks or up two flights of stairs or does not meet a MET level of 4
• Is inactive but has no limitations
• Is active: easily does vigorous tasks
• Performs regular vigorous exercises
PREOPERATIVE NONINVASIVE CARDIAC TESTING FOR RISK STRATIFICATION
There is little evidence to support widespread application of preoperative noninvasive cardiac testing for all patients undergoing major surgery. The current paradigm to guide the need for noninvasive cardiac testing is to perform such testing in patients with poor or unknown capacity if it would alter clinical management or modify perioperative care. Options for pharmacological stress testing include dobutamine stress echocardiography or myocardial perfusion imaging with coronary vasodilator stress (dipyridamole, adenosine, or regadenoson) with thallium-201 and/or technetium-99m. Routine screening with noninvasive stress testing is not recommended in patients at low risk for noncardiac surgery. Furthermore, coronary revascularization before noncardiac surgery is not recommended for the express purpose of reducing perioperative cardiac events. That said, revascularization before noncardiac surgery should be considered in patients if it would be indicated regardless of the surgery planned and instead according to clinical practice guidelines. In the Coronary Artery Revascular Prophylaxis trial, there were no differences in perioperative and long-term cardiac outcomes with or without preoperative coronary revascularization; of note, patients with left main disease were excluded.
RISK MODIFICATION: PREVENTIVE STRATEGIES TO REDUCE CARDIAC RISK
Perioperative Coronary Revascularization
Prophylactic coronary revascularization with either coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) provides no short- or mid-term survival benefit for patients without left main CAD or three-vessel CAD in the presence of poor left ventricular systolic function and is not recommended for patients with stable CAD before noncardiac surgery. Although PCI is associated with lower procedural risk than is CABG in the perioperative setting, the placement of a coronary artery stent soon before noncardiac surgery may increase the risk of bleeding during surgery if dual antiplatelet therapy (DAPT) (aspirin and thienopyridine) is administered; moreover, stent placement shortly before noncardiac surgery increases the perioperative risk of MI and cardiac death due to stent thrombosis if such therapy is withdrawn prematurely (Chap. 270). It is recommended that, if possible, elective noncardiac surgery be delayed 30 days after placement of a bare metal intracoronary stent and ideally for 6 months after deployment of a drug-eluting stent. Contemporary stent platforms allow for greater flexibility in the earlier interruption of DAPT; current clinical practice guidelines do suggest consideration of elective noncardiac surgery 6 months after drug eluting stent (DES) implantation if the risk of further delaying surgery exceeds the risk of stent thrombosis/myocardial ischemia. For patients who must undergo noncardiac surgery early (>14 days) after PCI, balloon angioplasty without stent placement appears to be a reasonable alternative because DAPT is not necessary in such patients.
PERIOPERATIVE PREVENTIVE MEDICAL THERAPIES
The goal of perioperative preventive medical therapies with β-adrenergic antagonists, hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins), and antiplatelet agents is to reduce perioperative adrenergic stimulation, ischemia, and inflammation, all of which are heightened during the perioperative period.
The use of perioperative beta blockade should be based on a thorough assessment of a patient’s perioperative clinical and surgery-specific cardiac risk (e.g., as with the RCRI). The paradigm for beta blockade in the perioperative period has shifted in recent years owing, firstly, to the publication of the PeriOperative Ischemic Evaluation (POISE) trial demonstrating that, while perioperative beta blockade reduces the perioperative risk for MI, this is at the expense of increased death and stroke. Regarding POISE, this trial has been criticized for the use of an excessive dose of beta blocker in the perioperative period and one that may not be reflective of clinical practice, nor one that was titrated in the days or weeks preceding the procedure or surgery. Secondly, research misconduct has discredited the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography (DECREASE) family of studies, which previously contributed to the bedrock of data supporting the use of perioperative beta blockade but have now been retracted.
Current guidelines emphasize the following key points:
Continuation of beta blockade in patients undergoing surgery and who have been receiving such therapy chronically.
Avoidance of beta-blocker withdrawal or initiation on the day of surgery.
Consideration of initiation of beta-blocker therapy perioperatively (ideally far enough in advance to assess safety and tolerability) in very select high-risk patients, namely, those with intermediate- or high-risk ischemia or three more RCRI risk factors.
HMG-COA REDUCTASE INHIBITORS (STATINS)
A number of prospective and retrospective studies support the perioperative prophylactic use of statins for reduction of cardiac complications in patients with established atherosclerosis. For patients undergoing noncardiac surgery and currently taking statins, statin therapy should be continued to reduce perioperative cardiac risk. Initiation of statin therapy is reasonable for patients undergoing vascular surgery independent of clinical risk. Perioperative initiation of statin therapy should be considered in patients undergoing elevated risk procedures if there is an indication for such therapy separate from the surgery and according to clinical practice guidelines.
ANGIOTENSIN-CONVERTING ENZYME (ACE) INHIBITORS
It is important to maintain continuity of therapy with ACE inhibitors (when such therapy is used for the treatment of heart failure or hypertension).
The 4- to 6-week period following implantation of an intracoronary stent (bare metal or drug eluting) constitutes the period of time of greatest risk for the development of stent thrombosis. If possible, noncardiac surgery should be avoided in this vulnerable period. The duration of DAPT thereafter is dictated by the circumstances in which PCI was performed and whether the indication was stable ischemic heart disease or acute coronary syndrome. For the former among patients treated with a drug eluting stent, dual anti-platelet therapy should be given for at least 6 months. For the latter, dual anti-platelet therapy should be given for at least 12 months. However, DAPT may be interrupted to allow for noncardiac surgery 30 days after BMS and 6 months after DES, respectively. If P2Y12 inhibitor therapy (clopidogrel, prasugrel, or ticagrelor) is interrupted or discontinued in patients who have received intracoronary stents, aspirin should be continued perioperatively (save select circumstances where the risk of bleeding may be catastrophic as in neurosurgical or spinal procedures) and the P2Y12 receptor inhibitor should be restarted as soon as possible post-operatively. Decisions surrounding antiplatelet management in the perioperative setting among patients who have received intracoronary stents are complex and should involve multidisciplinary decision-making.
Based on the results of POISE-2 (a large multicenter, international, blinded randomized clinical trial of aspirin and clonidine), α2 agonists for prevention of cardiac events are not recommended in patients who are undergoing noncardiac surgery. In this trial, clonidine increased the rate of nonfatal cardiac arrest and clinically important hypotension, while reducing the rate of death or nonfatal MI.
Evidence is lacking to support the use of calcium channel blockers as a prophylactic strategy to decrease perioperative risk in major noncardiac surgery.
Mortality risk is low with safe delivery of modern anesthesia, especially among low-risk patients undergoing low-risk surgery (Table 467-4). Inhaled anesthetics have predictable circulatory and respiratory effects: all decrease arterial pressure in a dose-dependent manner by reducing sympathetic tone and causing systemic vasodilation, myocardial depression, and decreased cardiac output. Inhaled anesthetics also cause respiratory depression, with diminished responses to both hypercapnia and hypoxemia, in a dose-dependent manner; in addition, these agents have a variable effect on heart rate. Prolonged residual neuromuscular blockade also increases the risk of postoperative pulmonary complications due to reduction in functional residual lung capacity, loss of diaphragmatic and intercostal muscle function, atelectasis, and arterial hypoxemia from ventilation-perfusion mismatch.
TABLE 467-4Gradation of Mortality Risk of Common Noncardiac Surgical Procedures ||Download (.pdf) TABLE 467-4 Gradation of Mortality Risk of Common Noncardiac Surgical Procedures
|Higher || |
• Emergent major operations, especially in the elderly
• Aortic and other noncarotid major vascular surgery (endovascular and nonendovascular)
• Prolonged surgery associated with large fluid shift and/or blood loss
|Intermediate || |
• Major thoracic surgery
• Major abdominal surgery
• Carotid endarterectomy surgery
• Head/neck surgery
• Orthopedic surgery
• Prostate surgery
|Lower || |
• Eye, skin, and superficial surgery
• Endoscopic procedures
Several meta-analyses have shown that rates of pneumonia and respiratory failure are lower among patients receiving neuroaxial anesthesia (epidural or spinal) rather than general anesthesia. However, there were no significant differences in cardiac events between the two approaches. Evidence from a meta-analysis of randomized controlled trials supports postoperative epidural analgesia for >24 h for the purpose of pain relief. However, the risk of epidural hematoma in the setting of systemic anticoagulation for venous thromboembolism prophylaxis (see below) and postoperative epidural catheterization must be considered.